Since 1979, we have treated a total of 29 children with advanced-stage B-cell tumours (diffuse undifferentiated, small non-cleaved cells): 18 stage III and three stage IV, according to a clinical staging classification (Murphy, 1980), and eight with B-cell acute lymphoblastic leukaemia (B-ALL). Treatment has been based upon appreciation of rapid tumour growth kinetics and has consisted of high-dose fractionated cyclophosphamide courses, vincristine, adriamycin and infusions of cytosine arabinoside (Ara-C) with intrathecal chemotherapy. The first 12 patients (1979-1981) received, in addition, superfractionated radiotherapy (twice a day) to the involved field (22.5 Gy) and the craniospinal axis (18 Gy). Since January 1981, radiation therapy has been omitted, and subsequent patients have received the same agents as above plus high doses of methotrexate coordinated with the escalating doses of Ara-C infusions. Toxicity has consisted mainly of universal, severe but reversible haematopoietic suppression with attendant febrile episodes. Complete-remission rate for all 29 patients has been 86%, with three early failures due to progressive disease and one death from infection. Overall disease-free survival for children with stage III disease has been excellent (78%). Initial involvement of central nervous system (CNS) and/or marrow is grave: none of three patients with stage IV lymphoma and only one of eight with B-ALL is surviving off therapy without evidence of disease, suggesting a need for alternative therapies for these cases. Results are significantly better than our historical institutional experience.